/* PeerCheckTasks - TimerTask that checks for good/bad up/downloaders.
   Copyright (C) 2003 Mark J. Wielaard

   This file is part of Snark.
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

package org.klomp.snark;

import java.util.*;

/**
 * TimerTask that checks for good/bad up/downloader. Works together
 * with the PeerCoordinator to select which Peers get (un)choked.
 */
class PeerCheckerTask extends TimerTask
{
  private final long KILOPERSECOND = 1024*(PeerCoordinator.CHECK_PERIOD/1000);

  private final PeerCoordinator coordinator;

  PeerCheckerTask(PeerCoordinator coordinator)
  {
    this.coordinator = coordinator;
  }

  public void run()
  {
    synchronized(coordinator.peers)
      {
	// Calculate total uploading and worst downloader.
	long worstdownload = Long.MAX_VALUE;
	Peer worstDownloader = null;

	int peers = 0;
	int uploaders = 0;
	int downloaders = 0;
	int interested = 0;
	int interesting = 0;
	int choking = 0;
	int choked = 0;

	long uploaded = 0;
	long downloaded = 0;

	// Keep track of peers we remove now,
	// we will add them back to the end of the list.
	List removed = new ArrayList();

	Iterator it = coordinator.peers.iterator();
	while (it.hasNext())
	  {
	    Peer peer = (Peer)it.next();

	    // Remove dying peers
	    if (!peer.isConnected())
	      {
		it.remove();
		continue;
	      }

	    peers++;

	    if (!peer.isChoking())
	      uploaders++;
	    if (!peer.isChoked() && peer.isInteresting())
	      downloaders++;
	    if (peer.isInterested())
	      interested++;
	    if (peer.isInteresting())
	      interesting++;
	    if (peer.isChoking())
	      choking++;
	    if (peer.isChoked())
	      choked++;

	    // XXX - We should calculate the up/download rate a bit
	    // more intelligently
	    long upload = peer.getUploaded();
	    uploaded += upload;
	    long download = peer.getDownloaded();
	    downloaded += download;
	    peer.resetCounters();

	    if (Snark.debug >= Snark.DEBUG)
	      {
		Snark.debug(peer + ":", Snark.DEBUG);
		Snark.debug(" ul: " + upload/KILOPERSECOND
			    + " dl: " + download/KILOPERSECOND
			    + " i: " + peer.isInterested()
			    + " I: " + peer.isInteresting()
			    + " c: " + peer.isChoking()
			    + " C: " + peer.isChoked(),
			    Snark.DEBUG);
	      }

	    // If we are at our max uploaders and we have lots of other
	    // interested peers try to make some room.
	    // (Note use of coordinator.uploaders)
	    if (coordinator.uploaders >= PeerCoordinator.MAX_UPLOADERS
		&& interested > PeerCoordinator.MAX_UPLOADERS
		&& !peer.isChoking())
	      {
		// Check if it still wants pieces from us.
		if (!peer.isInterested())
		  {
		    if (Snark.debug >= Snark.INFO)
		      Snark.debug("Choke uninterested peer: " + peer,
				  Snark.INFO);
		    peer.setChoking(true);
		    uploaders--;
		    coordinator.uploaders--;
		    
		    // Put it at the back of the list
		    it.remove();
		    removed.add(peer);
		  }
		else if (peer.isChoked())
		  {
		    // If they are choking us make someone else a downloader
		    if (Snark.debug >= Snark.DEBUG)
		      Snark.debug("Choke choking peer: " + peer, Snark.DEBUG);
		    peer.setChoking(true);
		    uploaders--;
		    coordinator.uploaders--;
		    
		    // Put it at the back of the list
		    it.remove();
		    removed.add(peer);
		  }
		else if (peer.isInteresting()
			 && !peer.isChoked()
			 && download == 0)
		  {
		    // We are downloading but didn't receive anything...
		    if (Snark.debug >= Snark.DEBUG)
		      Snark.debug("Choke downloader that doesn't deliver:"
				  + peer, Snark.DEBUG);
		    peer.setChoking(true);
		    uploaders--;
		    coordinator.uploaders--;
		    
		    // Put it at the back of the list
		    it.remove();
		    removed.add(peer);
		  }
		else if (!peer.isChoking() && download < worstdownload)
		  {
		    // Make sure download is good if we are uploading
		    worstdownload = download;
		    worstDownloader = peer;
		  }
	      }
	  }

	// Resync actual uploaders value
	// (can shift a bit by disconnecting peers)
	coordinator.uploaders = uploaders;

	// Remove the worst downloader if needed.
	if (uploaders >= PeerCoordinator.MAX_UPLOADERS
	    && interested > PeerCoordinator.MAX_UPLOADERS
	    && worstDownloader != null)
	  {
	    if (Snark.debug >= Snark.DEBUG)
	      Snark.debug("Choke worst downloader: " + worstDownloader,
			  Snark.DEBUG);

	    worstDownloader.setChoking(true);
	    coordinator.uploaders--;

	    // Put it at the back of the list
	    coordinator.peers.remove(worstDownloader);
	    removed.add(worstDownloader);
	  }
	
	// Optimistically unchoke a peer
	coordinator.unchokePeer();

	// Put peers back at the end of the list that we removed earlier.
	coordinator.peers.addAll(removed);
      }
  }
}
